Securing means for electrical high vacuum vessels



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Patented Sept. 20, 194g so 5..,frnr1es'esitaNr cierres SECURINGfM'EANSlFOR ELECTRICAL HIGH VACUUM VESSELSy Gunnar Johan Persson, Ludvika,A Sweden, as-

signor to Allmanna' Svenska Elektriska Aktiebolagct, Vasteras, Sweden, a Swedish corpora*` tion Applieation-.Septemher 26, 1946SerialNo..699,44il. In Sweden. September '2,7 1945 and a glass quality which do not attack, and are.

notyattacked. by such --vaporslas are frequentli7 contained in the high-vacuum space, for instance mercury vapor, and secondly' such difficulties which depend on the risk of spoiling or deforming` the yceramic body at the high/1temperatures necessary for the fusion of the glass; 'I'hes'edilfin culties, which, initiallycaused a Very large percentage of rejection of the joints made in the de.-i scribed way,. have been surmounted in.. avery high. degree 'by longer experience. For thi'sreason it' has now been found advisable to employ the aforesaid joining method also in such places in high-vacuum, where the glass layer has no sealing function, i. e. where it is surrounded by vacuum on all sides. Such an application of the said method of joining forms the object of the present invention.

The advantage of employing a joint of the aforesaid kind in places surrounded by vacuum on all sides instead of the detachable joint type which has been used before is in the rst line that it requires essentially less space than a detachable joint. In most high vacuum vessels, for instance electric valve or so-calledgas or vapor discharged vessels, the question of space is very important. It has also been found that by reason of the rigidity of the glass joint it is possible to obtain a very great precision which is of special importance for such parts which are kept under diierent electric potential in high-vacuum in order to maintain the mutual distances which give a maximum of breakdown voltage.

An application of the invention is shown in the accompanying drawing which shows an insulator bushing for an anode bolt of an ionic valve vessel having two metal parts secured thereto in a longitudinal section in Fig. 1 and in a cross section in Fig. 2, a vessel Il being shown in section at Fig. 3 surrounding the insulator and the metal parts thereon, and the end of a tube for evacuating the vessel being shown at l2. Fig. 4 is a detail ,2. cross-section showing the joint between the ce ramic 'bodyu and the `metallic support.

lv is the insulator bushing made-imma ceramicv material, for instance porcelain, and which for instance is carriedthrough the metal bottom lofY the evacuated valve vessel Il in a vacuum manner immediatelyibelow the portionv shown; in Fig: 1". 2Qis-theanode bolt traversing the insulator and which may be sealed thereto at the lower 4end of the insulator. The'anode bolt is surrounded inside i'fh'e vacuum vessel I-I` and above the insuA lator by' two metal sleevess', 4, the innerone 3` for' instance carrying a control grid 9 and the-'outer one di thev anode sleeven F01, `which is open atfits lower end. In several cases a larger number of' sleeves surrounding the bolt mary be present, for

instance fcrcarrying several grids ory `for screen.- ing purposes. As allv these sleeves andt the anode bolt itself frequently are kept at widely different potentiall values, it is-of utmost-importance thatl ther distance betweenl the said partsV isfkept'as closely as possibley to the value corresponding to a 'maximum-r of breakdown voltage. As the sleeves are generally rather long, this necessitates a great precision and rigidity of their supporting parts.

In order to achieve this result the supporting elements, in this form of the present invention, consist of rings 5 and 6 respectively of an appropriate metal alloy, said rings having a conical and a cylindrical portion, which are secured to correspondingly shaped surfaces on the insulator by glass joints. Parts of the cylindrical portions are, however, free from the insulator and serve to secure the sleeves proper 3, Il, which for economical reasons are generally not made from the same material as the rings, but for instance from pure iron, while the rings are made from an alloy, which has about the same coefficient of thermal expansion as the porcelain, for instance composed of iron, nickel and cobalt. Such alloys are available commercially, for instance under the names sivar and kovar. For facilitating a better control of the glass joint between the rings and the porcelain, the former ones are preferably perforated by a circular row of holes l, through which a portion of the glass mass may penetrate during the fusion as shown in Fig. 4. For facilitating a more precise joint between the rings and the sleeves 3, 4 detachably secured thereto. the said sleeves may be provided with longitudinal slits at their lower end and with weakening circular notches 8, so that the tongues formed be.. tween the slits may adapt themselves to the rings. In joining these parts together they are preferal bly mounted in a jig, which keeps the parts exactly in the desired mutual position. Also in melting the glass joints the rings and the porcelain are preferably kept in the right mutual position by means of a jig. The joint surfaces on the porcelain are as a rule ground in advance for obtaining the exact shape.

Experience has proved that it will be more easy to place the sleeves 3, 4 in the right position with respect to the porcelain in the now described manner than if secured directly to the porcelain by the detachable joints. Also the joints require less space as compared with the latter type, which is of special importance in ionic valve vessels.

I claim as my invention:

1. A high-evacuated vessel for electrical purposes having a ceramic insulator at least partly inside said vessel and comprising a support wholly enclosed within the vacuum space of said vessel made of a metal alloy having a coefcient of thermal expansion near that of the insulator, a'fused glass joint between said support and insulator, and a metal part of a material different from that of said support wholly enclosed within the vacuum space of said vessel and carried by said support.

2. A high-evacuated vessel for electrical purposes having a ceramic insulator at least partly inside said vessel and comprising an annular support wholly enclosed Within the vacuum space of said vessel surrounding said insulator and made of a metal alloy having a coeflicient of thermal expansion near that of the insulator, a fused glass joint between said support and insulator, and a metal part of a material different from that of said support Wholly enclosed within the vacuum space of said vessel and carried by said support.

3. A high-evacuated vessel for electrical purposes having a ceramic insulator at least partly inside said vessel and comprising an annular sheet metal support of angular section wholly enclosed within the vacuum space of said vessel made of a metal alloy having a coefiicient of thermal expansion near that of the insulator, a fused glass joint between said support and insulator, and a metal part of a different material from said support wholly enclosed within the vacuum space of said vessel and carried-by said support.

4. A high-evacuated ionic valve vessel with electrodes thereinand having a ceramic insulator traversing the wall thereof, a support wholly enclosed within the vacuum space of said vessel made of a metal alloy having a coefcient of thermal expansion near that of the insulator, a fused glass joint between said support and insulator, and a metal part of a dierent material from that of said support wholly enclosed within the vacuum space of said vessel and carried by said support.

5. A high-evacuated vessel for electrical purposes having a ceramic insulator at least partly inside said vessel and comprising an annular support inside said vessel surrounding said insulator and having a perforated portion closely adhering thereto, said support being made of a metal alloy having a coeilcient of thermal expansion near that of the insulator, a fused glass joint between' said support and insulator, and a metal part enclosed in said vessel carried by said support.

6. A high-evacuated vessel for electrical pur-- REFERENCES CITED The following references are of record in thel` file of this patent:

UNITED STATES PATENTS Number Name Date 2,015,484 Lilienfeld Sept. 24, 1935 2,431,144

Scullin Nov. 18. 1947 

